Mexico deports hundreds of immigrants found in 2 semi-trucks

After X-rays detect them, the immigrants are sent to a detention facility

The case, a reminder of dangers immigrants face, draws national attention in Mexico

The country's interior minister tours the "migrant's route" Wednesday

Expert: Mexican authorities beef up enforcement along the Guatemala border

(CNN) -- They stood and squatted for hours, crammed into two sweltering semi-trailers, clinging to ropes so they would not fall as the trucks traveled through winding mountain roads.

Mexican authorities say the more than 500 illegal immigrants they detained Tuesday wanted to reach the United States and each had paid $7,000 to get there.

But by Wednesday, a day after X-ray equipment detected them at a highway checkpoint, the majority of them had been deported to their home countries in Central and South America.

In a migrant detention center surrounded by high walls near Mexico's southern border, the remaining 23 immigrants, who hailed from countries as nearby as the Dominican Republic and as far away as Nepal, will wait as officials arrange their deportation.

Immigrant detentions are nothing new in the southern Mexican border state of Chiapas, where at least 25,000 immigrants were apprehended last year.

But the large number authorities found in two vehicles Tuesday was a startling reminder of the desperation that drives immigrants to risk dangerous conditions.

The case drew national attention in Mexico, where the country's interior minister announced he would begin following the "migrant's route" through Mexico on Wednesday. The three-day trip was scheduled to include meetings on immigration with local officials and his Guatemalan counterpart.

The vast majority of the immigrants detained Tuesday were from Guatemala, and all 410 of them had been handed over to Guatemalan police by Wednesday afternoon, according to Mexico's National Migration Institute. The 80 detained immigrants who hailed from El Salvador, Ecuador and Honduras were scheduled to be deported Wednesday evening.

The immigrants who hailed from the Dominican Republic, India, Nepal, China and Japan awaited their fate Wednesday in Tapachula, Chiapas, at the recently renovated 21st Century Migration Station, Mexico's largest immigrant detention center.

Experts say the passage of Central American immigrants through Mexico on their way to the United States is hardly a 21st century phenomenon.

Immigration of Central Americans into the United States began to grow in the early 1980s, said Demetrios Papademetriou, president of the Migration Policy Institute in Washington. And for at least 15 years, American authorities have been pushing Mexican officials to crack down on "transit migration."

"Going back to the 1990s when we start to engage Mexico, this has been one of the two main goals of our conversation," Papademetriou said.

But the Guatemala-Mexico border was easy to cross until recently, said Andrew Selee, director of the Mexico Institute at the Woodrow Wilson International Center for Scholars.

"There's more of a federal presence today than there's ever been, for two reasons," he said. "One, because Mexico has been trying to make a case that the country is secure, and that they're doing their part on terrorism and on illegal immigration; but also, in part, because Mexico is very concerned about crime on the southern border."

That hasn't stopped immigrants from embarking on the journey, despite the dangers.

"People are going to keep coming," Selee said. "As bad as the economy has been in the U.S. over the past couple years, there are still people willing to take the risk of not finding a job because they also see no prospects where they are."

Journalist Angeles Mariscal of CNNMexico.com contributed to this report.